Children ran everywhere in the courtyard of the low-income apartment complex; adults fell to the ground. Bullets flew. The killers wounded three youngsters, but for reasons police can't explain, it was 19-year-old McGraw they were after.

As McGraw lay in the center of the green square, the gunmen stood over him and fired again. He was shot 15 to 20 times in all.

The Sept. 15 killing was remarkable in that it took place in the most innocent of settings - the fifth birthday of twin boys. But it was unremarkable in that one of the guns brandished was an AK-47-type rifle - a powerful, rapid-fire weapon that has long been used in Third World conflicts but is increasingly being used in American street fights.

Figures from the Bureau of Alcohol, Tobacco, Firearms and Explosives, obtained by the Associated Press through public records requests, show a marked increase in the number of AK-type weapons traced and entered into the agency's computer database because they had been seized or connected to a crime.

The number of such tracings rose even while the federal assault weapons ban was in effect and has continued to climb since its expiration.

Since 1993, the year before the ban took effect, ATF has recorded a more than sevenfold increase in 7.62x39mm guns - which includes the original Russian-made AK-47 and a variety of copycats from around the world. The number of AK-type guns rose from 1,140 in 1993 to 8,547 last year.

Since 2005, the first full year after the ban's expiration, ATF has recorded an 11 percent increase in such tracings.

ATF says the increases in the first half of the 1990s are partly the result of wider usage of its weapons database by local law enforcement agencies. But after that point, the numbers reflect a real increase in tracings of AK-type guns, the agency acknowledged.

The numbers corroborate what police chiefs around the country have been saying: AKs and other so-called assault weapons are terrorizing their communities and endangering their officers.

The numbers are reflected in some of the most horrifying violence of the past year, including a deadly shooting rampage at a department store in Omaha, Neb.

They're reflected in the growing number of police forces equipping their officers with higher-powered guns to match the criminals' firepower.

And they're reflected in a single 72-hour period in September that started with the shooting of four Miami-area officers and ended in Kenner, La., in a drab apartment complex just outside New Orleans.

-- On Thursday, Sept. 13, Jose Somohano, a 37-year-old officer with the Miami-Dade police, was cut down during a traffic stop in suburban Miami by a man with an AK-type weapon. Three other officers - armed, like Somohano, with just handguns - were wounded, one of them suffering a bullet wound the size of a grapefruit in her leg.

By midnight, the gunman, Shawn LaBeet, had been shot to death by police after a huge manhunt.

Police have refused to say how many times Somohano was hit or how many shell casings were found.

The officer's wife, Elizabeth Somohano, had gone off to her job at an insurance company earlier that day, and just before noon, Jose's sister reached her at the office. "Have you heard?" she asked. Something was going on in the area Jose patrolled.

Elizabeth called his cell. She text-messaged him, over and over. She called her kids to see if they had heard from him. She checked the Internet to find out what was happening, and learned that officers had been shot and a gunman was on the loose.

A colleague of Jose's - one of his closest friends - called Elizabeth and told her to stay put. He showed up at her office, and when their eyes met, he broke into tears.

"He didn't make it," he told her. She screamed.

Later, she took some comfort in knowing that her husband had eaten lunch that day, which meant he must have seen the hot-pink note she had slipped into his lunch bag along with his chicken salad-on-pita sandwich: "I love you, macho man."

Days before the ambush, Miami Police Chief John Timoney agreed to let patrol officers carry assault rifles to help counter the use of such weapons by criminals. John Rivera, president of the Dade County Police Benevolent Association, pleaded for the same for officers in the Miami-Dade department, which protects more than 1.4 million people around the city.

"It's almost like we have water pistols," he said.

For years, only SWAT teams and the like carried AR-15s or similarly powerful weapons. But police forces nationwide have increased their firepower to match the criminals' arsenal - not only in urban areas such as Miami and Los Angeles, but in Waterloo, Iowa, Stillwater, Okla., Danbury, Conn., and Merced.

-- On Friday, Sept. 14, along the Tigris River outside Baghdad, an alleged Shiite extremist linked to roadside bombings was taken into custody with his AK-47s and grenades. In Afghanistan, in villages south of Kabul, troops arrested three suspected Taliban militants and confiscated their weapons, including AKs. And in Australia, a former soldier pleaded guilty to gunning down a photographer with an AK in a Sydney contract killing.

With AK-47-type guns used in wars and insurrections all over the world, some 250,000 people are said to be killed by such weapons each year, and more than 75 million are believed to be in existence. In Iraq alone, congressional investigators estimate 110,000 AKs bought by the U.S. for security forces there cannot be accounted for.

The AK was designed by Mikhail Kalashnikov and went into production in 1947, with its name standing for Avtomat Kalashnikova and the year.

"Once the Wall fell, these guns were everywhere," said Carlos Baixauli, an agent with ATF.

Kalashnikov, who is now 88 and still lives in Russia, has said he is proud of his invention but saddened it's been used by terrorists. He said he wishes he had invented something like a lawnmower.

Bullets fired by AK-47s travel at a higher velocity than those from many other weapons, and can do grievous damage to the body. Often they have enough energy to pass clear through.

Knockoffs of the AK can be bought from legitimate gun dealers for as little as $300 and are also available on the street. Original Russian-made models are more expensive. Normal ammo clips hold 30 rounds, but higher-capacity ones are also available.

Most of the AKs on American streets are semiautomatic, meaning they fire as fast as the gunman can squeeze the trigger. Fully automatic ones, common on the battlefield, require just one pull of the trigger to release a burst of fire.

A 2004 study by the Brady Center to Prevent Gun Violence concluded that the U.S. ban on AKs and other guns was successful, saying in the five years before its passage, assault weapons made up 4.82 percent of ATF crime gun traces, compared with 1.61 percent between 1995 and 2003.

Many politicians, police chiefs and gun-control advocates point to the expiration of the assault weapons ban as a reason for the spread of the guns. But many others argue that the law was so riddled with loopholes that it had little effect.

"The basic reason why gun-control laws fail is that they require the cooperation of a very unlikely source, and that is criminals," said NRA spokesman Andrew Arulanandam. "Each time you pass a gun-control law, the only people that are going to be affected by that law, the only people that are going to follow that law are law-abiding Americans."

-- On Saturday, Sept. 15, at the Glenwood Apartments in Kenner, Trinioucka Martin rose early and cooked all morning for her twin boys' birthday party - meatballs, fried chicken, baked macaroni, sandwiches. She had already ordered a cake with the youngsters' picture on it, hired a disc jockey and rented the inflatable castle and house.

McGraw woke up at his aunt's house across a highway from the apartment complex and had a hankering for something sweet. He wanted some cake.

At the party, after the crowd had dispersed and the officers arrived, McGraw lay dead on the ground near a sewer grate, his torso and lower body riddled with bullet wounds. Balloons still floated from ribbon; the "Happy Birthday" banner still hung.

No arrests have been made. McGraw was buried in a $450 grave against a chain-link fence in a crumbling New Orleans cemetery. The mound of dirt above his casket is littered with rocks and debris. There was no money for a marker.